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| United States Patent |
6,139,706
|
|
Adam
, et al.
|
October 31, 2000
|
Sputter cathode
Abstract
In a sputter cathode with a plate-shaped target (8) and with a
trough-shaped yoke (3), arranged behind the target (8), with middle web
(5) and with magnets (7, 7', . . . ) for producing a closed tunnel of
field lines (15, 15', . . . ) curved in an arc in front of the target
surface as well as with three sheet-metal blanks (9, 10, 11) consisting of
one layer of a compound plate e.g. of an aluminum/iron compound plate,
which blanks are placed into the plane between the target (8) and the
front surfaces (12, 13) of the trough edge of the yoke (3), which front
surfaces face the target (8), all sheet-metal blanks (9, 10, 11) of
magnetically conductive material together form gaps (a, a') extending
approximately parallel to the front surfaces (12, 13), which gaps (a, a')
are filled out between the sheet-metal blanks (9, 10, 11) by the other
layer (21) of the compound plate.
| Inventors:
|
Adam; Rolf (Hanau, DE);
Krempel-Hesse; Jorg (Eckartsborn, DE);
Bahr; Martin (Haundorf-Grafensteinberg, DE)
|
| Assignee:
|
Leybold Systems GmbH (Hanau, DE)
|
| Appl. No.:
|
207413 |
| Filed:
|
December 8, 1998 |
Foreign Application Priority Data
| Dec 11, 1997[DE] | 197 54 986 |
| Current U.S. Class: |
204/298.16; 204/298.17; 204/298.19 |
| Intern'l Class: |
C23C 014/34 |
| Field of Search: |
204/298.16,298.17,298.19,298.21
|
References Cited
U.S. Patent Documents
| 4405436 | Sep., 1983 | Kobayashi et al. | 204/298.
|
| 4525262 | Jun., 1985 | Class et al. | 204/192.
|
| 4572021 | Feb., 1986 | Aichert et al. | 204/298.
|
| 4865708 | Sep., 1989 | Welty | 204/192.
|
| 4964968 | Oct., 1990 | Arita | 204/298.
|
| 5415754 | May., 1995 | Manley | 204/132.
|
| Foreign Patent Documents |
| 196 14 487 | Oct., 1997 | DE.
| |
| 196 17 057 | Nov., 1997 | DE.
| |
| 196 22 607 | Dec., 1997 | DE.
| |
| 196 22 606 | Dec., 1997 | DE.
| |
| WO 95/12003 | May., 1995 | WO.
| |
Primary Examiner: Chaney; Carol
Assistant Examiner: Mercado; Julian A.
Attorney, Agent or Firm: Smith Gambrell & Russell, LLP
Claims
We claim:
1. A sputter cathode comprising a flat, plate-shaped target formed from at
least one part and with a trough-shaped yoke arranged spaced apart from
the target with a middle web and with a plurality of magnets for
generating closed tunnels of field lines curved in an arc in front of the
target surface, a plurality of strip-shaped or annular blanks of
magnetically conducting sheet metal placed in the plane between the target
and a front surface of a trough edge of the yoke, which front surface
faces the target, and with a portion of said blanks covering the area
above the front surface of the trough edge and of the middle web and with
further blanks covering a part of the area between the front surface of
the middle web and the front surface of the trough edge, all sheet-metal
blanks together forming gaps extending approximately parallel to the front
surfaces, wherein said plurality of magnets are inserted into the yoke
bottom and/or the trough edge or middle web and wherein said plurality of
blanks are formed of magnetically conductive material cut out of one layer
of a dual-layer metal sheet laminate and a second layer of said laminate
is formed of magnetically non-conductive material and bridges the gaps
between the plurality of blanks and stiffens the blanks.
2. The sputter cathode according to claim 1 wherein said one layer of said
dual layer metal sheet laminate comprises aluminum and iron.
3. The sputter cathode according to claim 1 wherein said one layer of said
dual layer metal sheet laminate comprises copper.
4. The sputter cathode according to claim 1 wherein said one layer of said
dual layer metal sheet laminate comprises non-magnetic material.
5. The sputter cathode according to claim 1 wherein said one layer of said
dual layer metal sheet laminate comprises magnetic material.
6. The sputter cathode according to claim 1 wherein said second layer of
said dual layer metal sheet laminate comprises copper.
7. The sputter cathode according to claim 1 wherein said second layer of
said dual layer metal sheet laminate comprises magnetic material.
8. The sputter cathode according to claim 1 wherein said second layer of
said dual layer metal sheet laminate comprises non-magnetic material.
Description
INTRODUCTION AND BACKGROUND
The present invention relates to a sputter cathode with a flat,
plate-shaped target formed from at least one part and with a trough-shaped
yoke arranged behind the target with a middle web or bridge and with
magnets for generating closed tunnels of electric field or flux lines
curved in an arc in front of the target surface. Approximately
strip-shaped or annular blanks of magnetically conducting sheet metal are
placed in the plane between the target and the front surface of the trough
edge of the yoke, which front surface faces the target, and with blanks
covering the area above the front surface of the trough edge and of the
middle web and with further blanks covering a part of the area between the
front surface of the middle web and the front surface of the trough edge
and with all sheet-metal sections together forming gaps extending
approximately parallel to the front surfaces.
A sputter cathode of the type in question is known (U.S. Pat. No.
4,865,708) in which segments of permeable material are arranged between
the target on the one hand and the magnetic yoke on the other hand in the
plane of the magnet rows, namely, below the plane of the front magnet
surfaces facing the target in order to concavely deflect the tunnel of
curved field lines forming in front of the target in order to make
possible in this manner a wider erosion trough on the target and therewith
a higher target service life.
Furthermore, a sputter cathode has been suggested (DE 196 22 606.6) with a
base cathode body with a plate-shaped target as well as with a magnet yoke
arranged behind the target and with two closed series of magnets with
different polarities arranged in an oval or rectangular configuration and
coaxially to each other in a plane parallel to the target plane.
Sheet-metal blanks or appropriately configured partial blanks of
magnetically conductive material are placed in the plane between the
target and the front surfaces of the magnets facing the target. Two of the
sheet-metal blanks or partial blanks have a frame-shaped configuration.
The two arced sections of the sheet-metal blanks uniting straight
longitudinal parts to each other have an edge course deviating from a
circular arc, e.g. an elliptical, parabolic or even irregularly arced edge
course so that the gap formed by two adjacent, arced sections has an
irregular course of width.
In addition, a sputter cathode has been suggested (DE 196 22 607.4) with a
magnet yoke arranged behind the target with two rows of magnets arranged
in oval or in rectangular configuration and coaxially to each other in a
plane parallel to the target plane with the magnets three sheet-metal
blanks or groups of partial blanks placed into the plane between the
target and the front surfaces of the magnets facing the target. Two of
these sheet-metal blanks or partial blank groups cover the area above the
magnets and the third sheet-metal section or the third group covers a part
of the area between the magnet rows and all sheet-metal blanks together
form two gaps extending approximately parallel to the magnet rows.
An object of the present invention is to arrange the magnets and the
segments in such a manner that on the one hand a flat and especially wide
erosion trough forms during the sputtering operation, the most optimum
target removal of metal occurs and that on the other hand the area between
the two parallel magnet tunnels forms as narrowly as possible.
In addition, the segments should be formed in such a manner that they can
be manufactured as economically as possible and that their rigidity is
dimensioned in such a manner that they can be installed into the cathode
without further supporting or holding means.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved if the blanks
of magnetically conductive material are cut out of one layer of a
dual-layer sheet laminate consisting of a suitable metal alloy, as for
example, an aluminum/iron compound plate. The other layer is formed by
magnetically non-conductive material and bridges the gaps between the
blanks of magnetically conductive material as well as stiffens the blanks.
Thus, the present invention features a sputter cathode composed of at least
one part that is a flat, plate-shaped target and with a trough-shaped yoke
arranged spaced apart; e.g., behind the target with a middle web or bridge
and with a plurality of magnets for generating closed tunnels of electric
field lines that curve in an arc in front of the target surface. There are
also a plurality of generally strip-shaped or annular blanks of
magnetically conducting sheet metal placed in the plane between the target
and a front surface of the trough edge of the yoke. The front surface
faces the target and a portion of the blanks cover the area above the
front surface of the trough edge and of the middle web. Further blanks
cover a part of the area between the front surface of the middle web and
the front surface of the trough edge. All of the strip shaped or annular
blanks together form gaps extending approximately parallel to the front
surfaces. The plurality of magnets are included or inserted into the yoke
bottom and/or the trough edge or middle web and the blanks of magnetically
conductive material are cut out of the one layer of a dual-layer sheet
laminate consisting e.g. of an aluminum/iron compound plate. The other
layer of the dual layer laminate is formed by magnetically non-conductive
material and bridges the gaps between the blanks as well as stiffens the
blanks.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention allows very many possible embodiments, and will be further
understood from the accompanying drawings illustrating certain embodiments
in detail in a purely schematic fashion:
FIG. 1 is a partial perspective view of one half of a cathode with the
target and the sheet-metal blanks shown only as fragments;
FIG. 2 is a sectional view through the cathode of FIG. 1 in which a row of
magnets is positioned into the bottom of the trough-shaped yoke; and
FIG. 3 is a sectional view through a cathode in which, in contrast to the
embodiment of FIGS. 1 and 2, additional magnets are arranged on the trough
edge.
DETAILED DESCRIPTION OF THE INVENTION
The sputter cathode according to FIGS. 1 and 2 comprises a trough-shaped
base cathode body 2 into which a likewise trough-shaped yoke 3 is
inserted. The yoke 3 comprises a web 5 dividing recess 4 in the yoke in
the longitudinal direction, the length of which web is dimensioned in such
a manner that an oval cooling conduit 6 with a rectangular cross-sectional
surface is formed. A closed series of cube-shaped permanent magnets 7, 7',
. . . are inserted into the bottom part of the yoke 3 in such a manner
that their side surfaces facing and turned away from target 8 arranged
above yoke 3 are flush with the bottom surface of recess 4 and the back
surface of yoke 3. Three sheet blanks 9, 10, 11 are inserted between
target 8 and yoke 3, of which blanks the two blanks 9 and 10 are provided
concentrically to one another and are designed as oval rings. The middle
blank is a strip-shaped blank 11 surrounded by the annular blanks 9, 10.
The blanks 9, 10, 11 consist of magnetically conductive material and are
electroplated onto a sheet of magnetically non-conductive material or are
fabricated from one layer of a sheet-metal laminate or of a dual-layer
sheet, in which instance the second sheet layer of magnetic material
remains unmachined.
Target 8 is arranged above magnetic yoke 3 with its closed series of
magnets 7, 7', . . . The target is customarily provided on its bottom
which faces the magnets with a permanent target base plate (not shown in
detail).
The three sheet-metal blanks 9, 10, 11 enclose two gaps a and a' between
themselves which can be dimensioned to be equally wide over their entire
length or can be designed in a tapering or widened manner. Field lines 15,
15', . . . are deflected more or less strongly as a function of the gap
width a or a' so that a closed tunnel of field lines 15, 15', . . . is
formed which is flattened and thus on the whole compensates the sputtering
rate and also improves the target utilization.
Standard magnetron cathodes consisting of a simple magnetic arrangement
(two rows of magnets with opposed polarity) generally produce in their
target a tapered sputtering trough. This trough as a rule becomes
narrower, the deeper it becomes. An advantage of the invention is that a
magnet field is formed which is different above the target surface and in
the target. The field above the target surface corresponds to that of the
standard magnetron cathodes. It runs approximately parallel to the target
surface and enters and exits on the two sides of the target. A so-called
roof field is generated.
In contrast to traditional cathodes without sheets inserted between the
target and yoke, a field consisting of at least two such roof fields 16,
17 is generated in target 8 in the case of the embodiment of the
invention. As a result thereof, the plasma is divided on the target
surface into several adjacent partial plasmas, strengthened by which, no
longer the middle area of each target half but rather their edge areas are
worn, which results in a significant increase of the target utilization
since the sputtering trough becomes comparatively wider therewith.
During the construction of a sputter cathode of this type, greater magnetic
excitations are required than in the case of traditionally constructed
sputter cathodes since a greater portion of the magnetic flux is conducted
in the yoke and the sheets and therefore not over the target surface. The
entire magnetic flux density must therefore be increased.
When the required magnets are positioned inside and outside (that is, on
the web and on the trough edge), the available space for the magnets is
limited by the outside diameter (installation dimension) as a rule. Only a
limited volume can be used for the installation of the necessary magnet
masses--depending on the geometric conditions. Since the magnetic field
distribution is significantly defined by the field discharge at gaps a, a'
when using the principle in question, the actual position of the magnets
is, however, relatively unimportant. It is therewith possible to integrate
the magnets into the bottom of magnetic yoke 3 without greatly changing
the relative field course. There is a comparatively great amount of space
available in the bottom of yoke 3 for the installation of magnets. Magnets
7, 7', . . . are therefore installed horizontally into the yoke bottom.
Since no magnets are necessary in particular on edge 12 of trough-shaped
yoke 3 and on middle web 5 in the cathode in accordance with the present
invention, these areas can be designed to be especially narrow, which
results in better target utilization.
A further increasing of the magnet masses can be produced by the
combination of magnets which are integrated horizontally as well as
vertically in the yoke and/or are placed on it (see FIG. 3). In addition
to the horizontal magnets installed in the bottom, the magnets 18, 18', .
. . are placed on the circumferential edge of yoke trough 19.
A dual-layer sheet or sheet laminate is advantageously used for the
production of sheet-metal blanks 9, 10, 11, in which sheet laminate the
one layer consists of iron and the other layer of copper, which two sheets
are permanently pressed to one another, welded, cast or rolled (plated)
onto each other.
The layer of iron is purposefully milled off from the copper layer 12 so
that blank 9, 10, 11, 21 shown in FIG. 1 is produced which is inherently
stiff, assures the accuracy of the size of gaps a, a', . . . and can be
readily installed into the cathode.
Further varations and modifications of the foregoing will be apparent to
those skilled in the art and are intended to be encompassed by the claims
appended hereto.
German priority application 197 54 986.1 is relied on and incorporated
herein by reference.
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